This invention relates to a method and an apparatus for measuring a stream of fiber tufts as it is advanced, for example, in a pneumatic conveyor duct in a spinning preparation plant. The fiber tufts pass by a measuring station which forms a measuring value subsequently applied to an electronic evaluating device for regulating or controlling th quantity of the fiber tufts in flight.
In order to regulate or control the flow of materials (such as fiber tuft streams) sensors have been needed which determine the passage of material and setting members which vary the throughput. In a known method flow-through scales or weighing plates have been used as sensors. As setting members rpm-variable drive motors are used which drive the conveyor rollers for the material. Such sensors, however, are not adapted for use in certain machines or systems because the sensors are incapable of measuring the fiber tufts in flight. Also, scale systems often may not be used because of lack of space.
According to another process, sensors are used which optically detect the fiber tufts in flight and the throughput is calculated by an electronic evaluating device. Such a system, however, was not found to be operationally satisfactory because no positive and sufficiently throughput-analogous correlations exist. According to still another known process, the conveying air stream is sensed by a pressure sensor and the pressure is monitored. The material throughput is determined from pressure and air speed changes which are representative of the material contents of the air flow. Such a system too has proven to be unusable.
Yet another proposal suggests a periodical deflection of the fiber tuft stream from the conveying duct, a separation of the tufts from the air stream and a weighing of the separated fiber tufts. For a given period of observation then the weight of the material is supposed to be determined. With such a system one may arrive at a long-range throughput under the assumption that the material stream varies only slightly in time. Such a system, however, is inaccurate and is not adapted for machine controls which are to ensure a disturbance-free operation.
All the above-outlined proposals have the particular disadvantage that they do not make possible an accurate measurement of the fiber tuft stream in a predetermined period and may not be used at any location where fiber tuft streams in fiber processing (spinning preparation) machines are present.